Pre-heating installations for boilers for quick heating and steaming



March 25, 1958v R, H. ROBINSON 2,8

' FEE-HEATING INSTALLATIONS FOR BOILERS FOR QUICK HEATING AND STEAMING Filed Nov. 22, 1948 IN V EN TOR.

PRE-HEATING INST ALLATIQNS FUR BDILERS FOR QUICK HEATING AND STEAMHNG Roy H. Robinson, Chicago, iii. Application November 22, 1948, Serial No. 61,514

15 Claims. (Cl. 122-68) This invention relates to improvements in auxiliary heating elements in boilers and heating plants disclosed in my co-pending application Serial No. 452,482, filed July 27, 1942, now Patent 2,455,192 and my Patent No. 2,291,921, issued August 4, 1942, and to improved methods of forming fabricating and installing same.

One of the principal objects of my invention is to provide simple and economically formed pro-heating and presteaming elements having batteries of quick heaters which can be facilely handled as prefabricated units particularly suited to quick installation in the fire-boxes of installed and operating boilers and with a minimum of fieldwork and installation time and expense while at the same time providing many beneficial features and results obtainable with more elaborate installations presented in my previous inventions as noted.

These and many other advantages of my invention will be better understood by referring to the following specifications when considered in connection with the accompanying drawings illustrating certain embodiments hereof of which:

, Fig. 1 is a transverse sectional elevation on the line 1-1 of Fig. 2 through the firebox of a typical boiler showing the pre-heating and pre-steaming battery installation.

Fig. 2 is a fragmentary longitudinal sectional elevation of same on the line 22 of Fig. 1.

Fig.3 is a fragmentary cross section showing in enlarged scale the construction of one of the battery preheating and pre-steaming units. 7

. Fig. 4.is a cross section through the connection of the preheating unit in the wall of the firebox.

Fig. 5 is a fragmentary cross section showing a modified form of the battery support and feed shown of Fig. 3.

Fig. 6 is a fragmentary cross section showing a modified form of the structure of Fig. 3.

Referring to the drawings in detail, Figs. 1 and 2 show cross sections of a typical heating boiler of the horizontaltype similar to many in common use in heating plants in apartment and other buildings. The water and steam compartments 1 and 2, respectively, are formed by the outer steel shell 3 and the inner steel lining of the firebox formed by the crown sheet 4 and the side walls 5, connected at the back with the boiler tubes 6. The water 7 covers the crown sheet for a few inches, as noted, in the customary practice. The floor of the firebox is formed in the case of hand firing by a grate but in this instance is shown an underfeed coal stoker, now quite commonly installed for the modern operation of such heating plants. This has a fire pot 8 spaced away from the side walls 5 and centered on the longitudinal axis of the firebox. The coal 8a is fed into the firepot by a screw feed 9 and forced draft is delivered through the tuyeres 10, the stoker being automatically operated in most instances and preferably by a pressure-stat 11, which is set to stop the operation of the coal feed and forced draft when the steam pressure reaches a point for which the pres-surestat is set and to start same again atent 1827,82 Patented Mar. 25, 1958 ice when the pressure falls to another set point. The stoker can similarly be automatically operated by a thermostat or an aquastat, or time clock, or a combination of any or all such or other automatic devices. The firebox is entered through the customary firing door 12, which is also available for hand firing. Oil, gas or other combustion substitutes may likewise be employed in lieu of the stoker.

In order to obtain the greatest and increased efliciency, I preferably provide within the firebox or in advance of the fines a combustion gas intercepting Wall 13 transversely thereof, and with a gas exit opening 14 spaced away from the cooling water jacket on all sides, and preferably formed of refractory material, such as firebrick, all in accordance with my co-pending application and patent above mentioned.

. The boiler stack 15 is preferably provided with a damp er control 16, together with a fly control 16a by which means the flow of the combustion gases in the firebox can be directed and controlled for the purpose of heating the pre-heating and pre-steaming elements, to be described, more efiiciently. When desired for still greater efliciency, a vacuum pump 17 is added to draw the steam through the pipe 18' and the return water returns to the boiler through the pipe 19. The steam passes into the heating system through the outlet 20.

Within the firebox, as noted, I introduce my pre-heating and pro-steaming battery units 21, each unit including a plurality of quick heating elements 22 preferably in the form of specially formed coils fabricated out of highly conductive metal such as copper for example. Any desired number of these battery units can be introduced into the firebox according to the size and nature of the firebox and the particular set-up preferred. Each quick heating battery has its multiple quick heating elements 22 operatively connected to and supported by or suspended from a simply fabricated structural element 23 which in turn operatively connects with the water and steam chamber throughthe side walls 5. This element 23 feeds water into the quick heating elements 22 through one channel and pre-heated water or steam back to the water and steam chamber through a second return channel and serves both to pre-heat the incoming water being delivered to the battery elements 22, support the latter in a span across the firebox and finally deliver the preheated water or steam in a complete circuit.

The multi-functioning element 23, forming the supporting portion of unit 21, is preferably in the form of a heat absorbing plate structure as disclosed in Fig. 3 or alternate Fig. 6. This not only presents an extensive heat absorbing and transmitting face to the heat rays and combustion gases for quick pre-heating and extended heating of the water transmitted to and from the coil or quick heating elements 22, but also provides, simultaneously, a strong structural span support to carry the load of the latter and likewise form conveyor channels for so circulating the water. It will be readily seen that this sheet metal or plate formed unit lends itself to facile and inexpensive fabrication by stamping the metal plates or strips 24 and 24a which also can be identical and pressed with a common die, and then joining them face to face as indicated. In this stamping, the intake and outlet openings, 24' and 24" respectively, are punched with the metal drawn to form projecting receiving flanges as shown to which the tubing ends of the coils 22 or their connections are brazed and preferably in the single joining operation'of general assemblage. In such assemblage, the plates 24 and 24a are held by a few assemblage rivets 25 or by tack or spot-welding at a few points as shown and then after complete assemblage, of the several and desired parts and elements, the whole is metallically sealedal'ong' the contacting faces and joints by dip brazing in a tank prdvided for such purpose. In lieu thereof, welding or other brazing may be resorted to in whole or part as desired. Themetal plates, so joined provide the feed channel 26 and the return channel 27.

These channels mayjheof an desired shape merges see;

tion but I preferabjly form them harrow .in -theii' cross width and longer the oppositedirection or height so that a'thin'b'ody'jof water passing through same is exposed to a large area of heat conducting' metal faces. A

further heating plate 28, stiffener and coil-support as;

of 29, so providing against undue sagging of the coils when in operation. It willbe'understood that in Fig; l six battery coils are included in the unit 21, the two on the right hand being removed in the drawing to better disclose the above construction of'the plate carrier 23. The number of coil, elements or pre-steamers in a unit can obviously be varied to suit preferred results for varied conditions and boilers.

A modified form of the unit 23 is shown in Fig. 6 where an unchannelled plate 246 is used for the main supporting member and backing. This has intake openir'igs 24' punched and drawn, as indicated, for receiving,

the coil connections for the lower i'ntake channel formed by the shaped metalstrip 24b riveted and brazed to the face of 24c while the upper outlet channel is likewise formed by the corresponding channeled strip 24d which has an extruded opening (not shown) for receiving the coil outlet connection the same as in Fig. 5. Also in place of forming separate metal channel strips 24b and 24d, a single metal plate or strip as 24 of Fig. 3 may be brazed to the backing metal plate 24c.

Also when desired, in lieu of the above stamped and brazed plates, stock pipe or tubing may be employed. Such an arrangement is shown in Fig. 5 where the pipe 31 is used for the lower intake feed and pro-heating line for the coils or heaters 22 and the pipe 32 for the upper return or steam line. Both of these pipes can be of high conductive metal such as copper or copper alloy but where theload carried by same, i. 'e., coils and water, and the span in the combustion chamber is such as to make it preferable, the upper pipe 32 can be of strong load carrying steel, high heat conductivity being less important in the return line, and the high conductive metal such as copper used for the lower pre-heating feed pipe 31, where the conductivity is of first importance. The lower pipe 31 is metalli'cally joined to the upper pipe 32 by metal straps, preferably copper, 33-, which are.

brazed to same and to themselves and locatedat spaced apart points, one to each coil. These straps, project downward with the hooked slotted apertures 29 and the flanged outpressed supports 30' for carrying the coils, sirnnections 31a and 32a, known in the trade. as Weldole ts still compact a nfger number within the length of a carry:

' provide extended pipe -or tube connections 44 and 1 5 to iug unit 23, I preferably make the coils of somewhat rectangular shape, narrow in width and wider in depth overhanging the firebed, as indicated. So as to expose more metal to the rising combustion gases and radiant heat rays, I also preferably tilt the coils forward, also sideways, as shown, so as to help avoid. adjacent coil turns bathing one another as occurs when in vertical positioning. Also in tipping the coils forward, I am able to. compact my prefabricated unit 21 (which must he formed to pass the boiler firebox doors), connecting my water intakes to the back of 23 and the upper outlets to the front thereof. This also permits easy access to the railway unions 34 both top and bot-toml. These are preferably included and brazed in connection with the openings 24' and 24" and the coil ends'in the dip braza supporting element 23 to better resist sagging as well improve compactness, I To further stiffen the coils 21? against sagging as well as produce faster heating of same, high conductive metal stiffeners 35 are preferably braied to sides of the coils at each turn. These are also {pi-eferably placed atthe sidesof eachvcoil as shown, so as to face the fire and combustion gases broadside, although any number of same may be added at other points about the coil.

Referring further to the heating and supporting plate uni-t 23, this has its channels 26 and 27 tapered near the ends and shaped in press-forming to receive and embrace round pipe nipple connections 36 which are brazed into samein the dipping process (or otherwise). At the other ends of the round connections 36 are likewise braz ed railway unions 37 which in turn form brazed conneeti ns' with the intake and outlet pipes 38 and 39, respeet ive1 These latter can be provided many desired lengths to connect as above noted with unit 23' and these being the variable elements permit prefabricat-ing the units 2311'! pipe connections 38 and 39 are distorted andshapedm; the outwardend so as to fit into and substantially'fillj single collar connection 40, as shown for example in 1 Fig. 4. Pipes ;38 and 39 are so brazed into the eel'lar about their surfaces 25 and the connection 40hasashitably wide' face flange 42 to cover and extend over a c nection hole 41 which is cut in the water ehanfber wan '3 to receive the connection; The latter-with twoway intake and outlet is then welded to the iwallS around its perimeter and sealed by this weld 43. ie'ach' 'casic,

a 'double vconnection is secured by cutting but a single hole in the water chamber wall, saving 'b'o'ththe'timeand expense of a plurality of wall holes, otherwise necessary, and an entire battery unitv 21 is installed with the cutting of but two holes in the boiler wall. much more expensive field labor and th'e time of shut= down in an operating heating plant while installation is being made. After these connections 40' are welded in place, the prefabricated factory assembled units 21 are shoved through the firebox :door and connected in a few minutes to the railway unions 37,, ready for operation;'

' These connection pipes 38'and 39 which support the entire units 21 in connecting to' 23may be of any desired metal but I preferably make the upper one :39 of strong structural steel to better c'arrythe load and the Iowero'ne 38 of high conductive metal such as copper or its alloys. In my preferred form, although not necessarily, 'I' further connect with the connection '40 and extend u wartl'in the water chamber so that water intake '44 feeds onlythe hot test water from near the t'op of the water body 'thr'ouh its end opening 44' into the unit 21 while at the same time the steam produced thereby iscarriedjthrough his:

char e pipe 45direct to the up er steam space a without This minimizes the;

being cooled and mixed with the water by being directly discharged into same at 40. 'The pipe 45 is also pro vided with a water outlet hole 46 on its side, slightly below the water level above the crown sheet 4 so that when steam is not being produced and circulated by the coils, the preheated water fro-m these batteries can keep circulating with delivery and intake of the hottest waters at the top of the water chamber. This may occur in rest periods in the boiler firing, as governed by the automatic controls or before steaming temperature has been reached in the coils. It will be understood under these conditions the faster the water is so circulated fro-m the coils, the quicker the water temperature is raised in the top of the water body whereby steam is more quickly produced from it.

These pipes 44 and 45 are pre-cut to proper length for the particular boiler being equipped and are preferably flattened above their base at 40 so as to more readily bend in being pushed through the wall opening 41. They can also be made flexible for such purpose, if desired, and can be of this soft copper when preferred. These are joined with telescope connection with the respective pipes 38 and 39 at the point 47. Where they are of short length this connection may be brazed or otherwise secured at the factory. Where of too great length for such insertion through the water chamber wall opening 41, however, they can be shoved through same independently and then brazed or weld tacked to 38 and 39 by pulling forward through the Wall opening for this joining. The hole 41 is out large enough to facilitate this and within the coverage later provided by the flange 42.

Referring further to the construction of the supporting units 23, the back plate 24a of Fig. 3 or 240 of Fig. 6 may be of strong load supporting steel or possibly aluminum alloy where weight reduction is preferred. Where cost is of greater concern, both plates 24 and 24a may be made of steel but for greater heating efficiency high conductive copper is the preferred metal for 24 in combination with steel plate 24a, or for even still greater heating efficiency 24a may also be copper of sufficient strength for the load. The same arrangement applies to the corresponding elements of Fig. 6. Similarly copper is preferred for forming the quick heating elements 22, preferably in coil form but where a particularly light unit is desired or where long span units are employed with a large number of coils, both the coils or their equivalents and the support.- ing units 23 may all be formed of suitable aluminum or aluminum alloy. Also as regards the units 23, the front plates or sheet metal strips may be of thinner gauge for quick heating whilethe back plates are of thicker gauge for supporting strength as indicated in Fig. 6.

Where firebox conditions permit and for the still greater efiiciency, I prefer to. combine my units 21 with a refractory heat and combustion holding wall introduced across the firebox and properly spaced away from the receiving combustion flues 6 and provided with a mixing and compression exit opening spaced away from the cooling walls of the water chamber on all sides. This restricted opening, as in the case of my previously mentioned patent and application, prevents the quick escape of the burning gases, so prolongs their heating action on the units 21, raises and maintains the temperature of the firebox containing same and serves to perfect combustion before the gases, partially chilled as they are by the units 21, escapein otherwise incompletely burnt condition into the flues. Instead this restricting opening mixes the hot and chilled gases together, compresses them in exit and restores combustion temperatures in whole or part, thereby. In the present case, as shown in Figs. 1 and 2, this intercepting refractory wall 13 with gas exit 14 is introduced into a typical Kewanee type of boiler in common use in which a cross water pipe 48 connects the opposite water legs of the firebox and supports a firebrick smoke baffie 49 on top of same. Utilizing this or proiding similar arrangement, applicant connects a brick base 50 with closures 51 of firebrick extended to 48 to form a barrier wall but leaving a central opening 14 for the main combustion exit, as noted, the size of which will be determined in relation to the draft, size of firebox, etc. These closures or slabs 51 can be cemented in place, edge to edge or be made removable at will for boiler cleaning if desired. Furthermore, to augment the exit opening 14 and more widely distribute the escaping gases in relation to the coils 22 and the fines 6, the closures 51 can be, and as shown in the present case, slightly spaced apart at their adjoining edges to form secondary and small exit slot openings 14 which operates in relation to the gases with similar functioning and manner as the main exit 14, mixing and compressing the hot and cold gases and so as to help promote the final combustion of the latter.

To further the control of the combustion gases generated by the stoker and transmit a maximum degree of heat to the quick heating, presteaming batteries 22, the boiler stack is also preferably provided with damper 16 and fly 16a as already mentioned. If this damper is suitably adjusted toward a closed position and the fly opened to the desired point While the forced air draft projected by the stoker apparatus into thefirebox from the tuyeres 10, the course of the burning gases from the coal bed 8a can be controlled at will and substantial portions of same projected upward to better engulf and circulate through the batteries 22 before looping downward to the exit openings 14 and 14' where they are again reheated in mingling with the hotter gases coming directly to these ports.

By these several means functioning in combination and through such related arrangements it is possible to pro duce steam quickly from the super-heated top of the water body of the boiler without waiting to raise a much larger portion of such water to the steaming point as in conventionally operated boilers. With the automatic onand-oif controls in operation it will be seen that the periods of fuel feed are so cut down with corresponding economy as well as much quicker steaming while smoking and poor combustion are largely eliminated. At the same time the heating capacity of the plant is greatly increased and an otherwise inadequate plant may be made to serve larger radiation and increased duty. While coal and stoker feed is shown in the drawings, any fuel may,

be employed as gas or oil for example, or even hand fired coal.

The units 21 may also be used in any desired number and with any desired number of pro-heating units 22 in each battery. The carrier unit 23, while shown in a vertical position in the drawings, may also be tilted at any angle from vertical to approaching horizontal as will best be determined by the position of the fire or the course of the fuel and combustion feed, and, as in the case of oil fuel, the direction and source point from which the burning fuel is projected or emanates. In Figs. 1 and 2, two six coil units 21 are employed, the two right side coils of Fig. 1 being removed to better disclose the construction of the carrier unit 23. It will also be understood that while the units 21 are in this case employed primarily to produce steam and quick steam, they are similarly serviceable where a hot water system is used in lieu of steam where they serve the same purpose to more quickly and economically heat the water for circulation through the heating system.

While the units 21 have the carrier element 23 connected to the side walls of firebox, connections may be made otherwise and particularly from the ends of 23 upward directly into the water above the crown sheet with connection 40 at each end welding directly into holes 41 'cut in the crownsheet or overhead metal plating, after the manner of my above noted pending application, instead of in the side walls as shown in Fig. l.

1 am aware that various changes and modifications may be made in my invention as shown and described without departing from the and I reserve the right to make all such variations as fairly fall within the scope of the following claims.

I claim as my invention: 1 r a 1. For use in the combustion chamberof a water heating plant, a quick water-heating portable unit suitable for passage through the door of said combustion chamber and including a supporting structural plate having formed therewith longitudinally disposed channels for water intake and return strutted apart by and in fixed and rigid union with a structural web and arranged for operative connection with the water chamber of said heating plant and, in addition to said web, a plurality of quick heating coils operatively connected with said channels. 7

2. For use in the combustion'chamber of a boiler and as an extra and additional adjunct thereto, a quick waterheating portable unit suitable for passage through the door of saidcombustion chamber and comprising a metallic supporting plate having a plurality of water conveying channels providing. intake and outlet passageways principles and spirit of my invention formed therewith and a battery of quick heating coils suspended from said plate and having their ends operatively connected with said intake and outlet channels so formed with said plate. V

3. In combination, a plurality of elongated metal strips joined together to form a heat absorbing and beam-like supporting metal unit with longitudinally disposed spaced apart Water channels formed therewith and with rigid structural Web connection between said channel portions at least at intervals along their length and a plurality of quick heating units operatively connected with said channel portions andwholly supported by said metal strips and being in addition to said web connection between said channel portions.

'4. The structure of claim 3 and employing said metal strips and forming the wall of at least one of said channels with adjacent longitudinally disposed metal wall sections of different metal having different physical properties, one of which possesses substantially higher heat conductivity, as compared with steel, and the other or" which possesses substantially higher structural strength for load support, as compared with copper.

5. In combination, a tubular pre-heating and supporting girder-like carrier with a web portion at least at intervals along itslength and'suitable for quick installation in the firebox of a heatin plant, a single two-way water connection at each end of said carrier for operative junction with the shell of the water chamber of the heating plant and a plurality of tubular coils operatively attached to and wholly supported by said carrier and being in addition to said web portion and designed to circulate water from andto said connections and through tubular portions of said carrier.

6. In combination with a metal plate-girder carrier unit having adjacent tubular passages extending longitudinally thereof and a structural web portion between same at least at intervals along their length, at least one operative connection suitable for attachment and entrance to the water chamber of a heating plant from the firebox thereof, said connection being interiorly divided for both receiving and returning water through same, and a battery of water circulating elements operatively connected to said tubular passages of said carrier unit and separate from said web portion and designed to circulate water fromand to said connection. v r e 7. For use in the combustion chamber of a heating plant and operative connection with the water chamber thereof, a quick water-heating unit suitable for passing through a door of said combustion chamber comprising a structural beam-like supporting carrier having upper and lower tubular sections rigidly united with'an interposed non-tubularrigidly connecting structural web portion and, in addition to said web portion, rigidly connected thereto, a plurality of quickheating tubular coils operatively connected to said tubular sections and at least rimarily supported by-said carrier.

8. For installation in the combustion chamber of a heating plant and operative connection with the water chamber thereof, a quick heating unit including a structural carrier fabricated as a rigidly integrated structural unit with longitudinally disposed tubular passages as a part thereof and a battery of quick heatingtubular coils disposed in front of and operatively connected with and suspended from same, and means, in addition to such operative connection, for supporting said suspended coils against sagging, including bearing supports, on which said coils bear, in the lower portion of said carrier, the

coils and in combination therewith a refractory barrier and closure wallcrosswise of the combustion chamber disposed between said coils and the gas exitend of said chamber, said wall being provided with spaced apart restricting escape apertures for the combustion gases including a main aperture spaced away from the walls of the water chamber and minor apertures spaced away from said main aperture and disposed to'guide portions of the escaping combustion gases closer to coils located at more distant points fromthe central portion of the combustion chamber and so permit efficient inclusion of a greater number and a wider distribution of coils carried by said support.

10. In a heating planthaving a combustion chamber and a water chamber, a plurality ofquick water-heating units disposed in said combustion chamber and operatively connected with said water chamber and a refractory wall barrier bi-secting said combustion chamber and interposed between said units and the combustion gas escapeway,

such as the flues, and a plurality of restrictive escape apertures, forming gas exits through said wall barrier and spaced awayfrom the shell of said water chamber for mixing, limiting and distributing the flow of the escaping gases and guiding portions of saidgases closer to heating units located at more distant points from the central portion of the combustion chamber and so permit inclusion of a greater number and a wider distribution of more efticient heating units in said combustion chamber.

11. The structure of claim 1 and having at least a plurality of said coils positioned with their upright axes non-parallel to the upright axis of said supporting structural plate.

'12. Of the class described, for use in the combustion chamber of a boiler and as a readily insertable adjunct thereto, a metallic girder-like supporting plate for spam ning said chamber and having a plurality of water conveying channels formed therewith and forming a structural load carrying portion thereof and'a battery of quickheating units suspended from said plate and having their ends operatively connected with intake and outlet channels so formed with said plate. I

13. The structure of claim 12 and having a plate projecting into the interior of at least one ofsaid channels to form a heat conductor and a stiffener, said plate extending outward of said channel to form a projecting heat absorbing fin.

14. The structure of claim 12 and having at least one of said channels having its wall formed with metal substantially stronger than copper for at least one longitudinally extending portion of said wall and with another metal which is relatively quick heating, as compared with steel, forming an adjacent longitudinally extending portion of said wall.

15-. For use in the combustion *chamberof a waterheating plant having a water chamber in conjunction with said combustion chamber, a quick water-heating unit including a plurality of longitudinally disposed tubular portions forming water-conveying channels of substantial length and joined to each other by fixed, rigid structural connection at least at intervals along theirlength to form a strong load supporting element and a plurality of quickheating tubular coils at least primarily supported by said element and operativcly connected to said tubular portions and being in addition to said structural joining of the latter, the unit being designed substantially to span the combustion chamber and operatively connect to the shell of the water chamber and be quickly and readily inserted in an existing plant, said unit furthermore being in combination with tubular extensions designed to extend upward within the water chamber of said heating plant and having openings at least adjacent their upper extremity for both drawing feed water for the quick-heating unit from the upper, hotter zone of the water body in said water chamber and delivering and returning steam at least adjacent to space left above said water body for holding steam, and from both ends of said unit through a single opening in the shell of the water chamber for each of the respective ends of said unit, at least one of said tubular extensions connecting with the water conveying channel forming the feed line of said unit and terminating with intake opening in said upper zone of said water body and at least one of said tubular extensions connecting with 10 the water conveying channel forming the outlet line of said unit and terminating with outlet opening above the water-line of said water chamber and having another opening located below said water-line and in said upper zone of said water body.

References Cited in the file of this patent UNITED STATES PATENTS 352,464 Green -2 Nov. 9, 1886 743,825 Burger et a1 Nov. 10, 1903 1,141,067 Lloyd May 25, 1915 1,406,729 Hallander Feb. 14, 1922 1,577,838 MacLean Mar. 23, 1926 1,732,304 Hawley Oct. 22, 1929 1,767,652 Daley June 24, 1930 1,775,079 Jones Sept. 2, 1930 1,840,575 Flower Jan. 12, 1932 1,856,963 Martin -3--- May 3, 1932 1,911,375 Tuche May 30, 1933 1,919,506 Glenn July 25, 1933 1,977,637 Kerr et al Oct. 23, 1934 2,016,276 Crosiar Oct. 8, 1935 2,104,229 Kelly Jan. 4, 1938 2,291,921 Robinson Aug. 4,' 1942 2,455,192 Robinson Nov. 30, 1948 FOREIGN PATENTS 12,842 Great Britain June 8, 1898 

